New York

New York has made a lot of the digital age. The city hosts a thriving tech sector with 300,000 employees -- on par with Silicon Valley -- and city government is praised for its use of analytics in evaluating all manner of programs.

Its signature environmental initiative -- PlaNYC -- contains hundreds of objectives on everything from the number of breakwaters made from oysters to cubic feet of natural gas captured from sewage plants. As former mayor Michael Bloomberg would say: "In God we trust. Everyone else, bring data."

Current Mayor Bill de Blasio seems intent on keeping this emphasis on numbers, and he's expanding the city's environmental initiatives as well -- recently announcing a pledge to cut carbon emissions 80% by 2050, largely by increasing energy efficiency in buildings.

Other innovations that put New York at the top of our list include a push for micro-apartments and affordable housing, redesigning streets to make them bike and pedestrian friendly, and pioneering the use of social impact bonds to attract private money into public projects. (Photo: Anthony Quintano/Flickr) --S.H.